Doctor blade and mounting



Nov. 8, 1949 Filed Dec. 21, 1945 H. A. BAKER 2,487,409

DOCTOR BLADE AND MOUNTING 2 Sheets-Sheet l Herberf A Baker Gum no Filed Dec. 21, 1945 Nov. 8, 1949 BAKER 2,487,409

DOCTOR BLADE AND MOUNTING 2 Sheets-Sheet 2 Patented Nov. 8, 1949 DOCTOR MOUNTING Herbert A. Baker, Boston, Mam. minor to Vickerys Limited, London, England, a corporation of Great Britain Application Decemberzl, 1945, Serial no. 636,334

. 2 Claims. 1

It is the primary object of this invention to improve the doctor blade construction disclosed in the patent to Vickery.1,912,605 and such improvement provides not only more efiective behavior of the doctor blade itself but also results in greatly increased economy of operation.

The above and other objects will be made clear from the following detailed description taken in connection with the annexed drawings in which:

' distinctly a consumable element and-must'i'requently be replaced. Accordingly, any economy in the cost of replacement blades is a material contribution to the economy of the installation.

Referring now to Fig. 1, there is shown a blade holder ID in which is mounted a blade l2 having one edge l4 bearing against roll IS. The opposite edge iii of the blade I: rests in a groove 20 in the Figure 1 is a cross section illustrating the genholder 10. Adjacent to groove is an upper eral relationship of the blade, of the blade holder supplementary groove 22 and a lower suppleand the roll; mentary groove 24.

Fig. 2 is a plan view partially in section show- The parts just described are shown on a larger ing the. relationship of the blade and holder; scale in Fig. 3 in which it will be noted that the Fig. 3 is a section on the line 3-3 of Fig. 2; 5 groove 20 provides considerable clearance above Fig. 4 is a perspective view of the portion of the locking strip; and

Fig. 5 is a section similar to Fig. 3 but showing a modified construction.

The use of doctors on paper machines involves problems which are not encountered in any other use to which doctors are put. Thefirst and most striking problem arises out of the extreme width encountered in the various rolls of paper machines and consequently the extreme length of the doctor. This may run in excess of 300 inches and obviously quite difl'erent conditions may be encountered from one end of the blade to the other. The second problem lies in the extreme surface speeds of the rolls to be doctored which 1 are frequently as great as 1,500 feet per minute and, in some of the light weight papers, over 2,000 feet per minute. The efiect of this surface speed is to generate a great deal of heat at the line of contact between the roll and the blade.

'The third problem arises out of the fact that paper making machines by their very nature are required to operate continuously for long periods and any interruption of production involves serious economic loss.

.The patent to Vickery 1,912,605 was an outstanding contribution to the art since it marked the first recognition of the principle which has now become the standard of the industry, namely,

the upper surface of the edge I8 of-the blade l2. This permits free longitudinal fiexure of the blade to permit the active edge I4 to conform to variations in the surface of the roll I 6. A thin flexible strip of spring steel 26 having a length substantially equal to the blade I 2 rests in the lower groove 24. Along strip 26 there are provided pro-v jections 28 in the form of rivets. These projections pass through apertures 30 in the blade I! and into the upper groove. The apertures 30 are preferably elongated in'the direction of blade length and are of a width to provide a distinctly v loose fit around the projections 28.

Fig. 5 illustrates a modified form of holder 40 having a groove 42 to receive the rear edge l8 of the blade II. The holder 40 is provided with a lower auxiliary groove 44 but has no upper groove corresponding tov the groove 22 of the holder iii. A strip 46 having projections 48 rests in the groove 44 with the projections 48 passing through apertures 30 in the blade l2. The projections 48, however, do not penetrate substantially beyond the upper surface of the blade I 2 and the holding of the blade against transverse withdrawal is, therefore, accomplished entirely through the lower groove 44.

While the projections have been illustrated as rivets, it is clear that bolts, struck up tongues, cotter pins, welded lugs or any other form of that the blade is to be brought into accurate conprojection might be used without departure from formity with variations in the surface of the the spirit of this invention. In Figs. 4 and 5 roll being doctored. The patent is further notethe thickness of the strips 26 and 46 has been worthy in combining of the application of the exaggerated. in order to bring out the fact that principle aforesaid with a locking of the blade the side edges of the strips are preferably rounded against transverse withdrawal from its holder 50 to minimize the chance of-the strips sticking in while permitting sliding and endwise removal of the grooves or becoming packed in the grooves by the blade from the holder. The present invenfine dust turned up by the blade.

tion improves on the Vickery construction by pro- It will be clear from, the foregoing that this viding a doctor blade in which there are no ininvention provides a blade which may be manucreases of thickness and which may beproduced factured, stored and handled at absolute minimum cost. The strips 26 and 46 with their projections are permanent parts of the installation so that the cost of the locking means has been transferred from the consumable blade element to a permanent portion of the installation. Since a great many doctors are used on a single paper machine and since the life of the blade is relatively short, this is a factor of considerable importance in the cost of annual operations. In addition this construction provides for the first time a flexible doctor blade of uninterrupted cross section and a support in which both edges of the blade enjoy complete freedom of flexure.

The flexibility aflorded both edges of the blade meets the problem of variations in the roll surface occurring over the great length of the blade. The uniformity of thickness provides a maximum opportunity for the dissipation of heat and for the equalization of temperature between the front and rear edges of the blade, while the relatively loose fit of the parts expedites blade changes and, therefore, shortens monthly or 7 annual shut-down time and decreases the quantity of defective paper occasioned by the changing of blades. The present invention, therefore, attacks directly the three major problems encountered by doctor blades, namely, the problem of length; the problem of surface speeds and the problem of continuity of operations.

While certain specific embodiments have been disclosed herein it is not intended that this invention be limited to the precise details disclosed but only as set forth in the subjolned claims which are to be broadly construed.

I claim:

1. A doctor for use in connection with the rolls of papermaking machines, comprising a holder provided with a recess along its length adapted to receive one edge of a doctor blade, grooves opening into the opposed walls of said recess, a narrow, elongated strip of resilient metal slidably received between the walls of one of said grooves and having a plurality of spaced projections fixedly secured thereon and extending across said recess into contact with a wall of the other groove, and a doctor blade in said recess and provided with'spaced apertures each loosely passing one of the projections on said strip.

2. A doctor for use in connection with the rolls of papermaking machines, comprising a holder provided with a recess along its length adapted to receive one edge of a doctor blade, a groove in said holder communicating with said recess, an elongated strip of resilient material slidably received between the walls of said groove and having a plurality of spaced projections fixedly secured thereto and extending into said recess, and a doctor blade in said recess provided with a plurality of spaced apertures each loosely receiving one of the projections on said strip.

HERBERT A. BAKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,552,363 Vickery Sept. 1, 1925 1,935,164 Russell Nov. 14, 1933 1,993,352 Schwartz Mar. 5, 1935 2,077,816 Vickery Apr. 20, 1937 2,329,277 Lodding Sept. 14, 1943 

